It’s a style. It’s a matter of fashion. In most western countries a black hat is considered a very formal hat worn only by persons of importance at special occasions, e.g. by royalty at a royal wedding. If black fedora became something associated with being lower class (e.g. if construction workers and garbage collectors wore black fedoras), the style would change.
Socks are a good example of how fashions changed. In 19th century Europe, white socks were a very important garment (remember, this is prior to paved street being common, and when horses tended to make the street dirty). Only rich people could manage to go with shoes (other than boots) and white socks. In America it’s opposite since white socks are preferred only for recreational or physical work and are distinctly undress – and you will notice that the percentage of frum people wearing white socks on Shabbos has fallen noticably over the last two generations.
Fashion is how you communicate to the world who you are and how you perceive yourself and how you want to be perceived. It has nothing to do with halacha or kabballah. Most frum Jews are communicating that we are respectable people who are very traditional in our outlook. A black hat does that.